Melosh, H.J., 2020. The Australasian tektite source crater: Found at last? Proceedings of the National Academy of Sciences 117, 1252.

http://www.pnas.org/content/117/3/1252.abstract Commentary on: Sieh, K., Herrin, J., Jicha, B., Schonwalder Angel, D., Moore, J.D.P., Banerjee, P., Wiwegwin, W., Sihavong, V., Singer, B., Chualaowanich, T., Charusiri, P., 2020. Australasian impact crater buried under the Bolaven volcanic field, Southern Laos. Proceedings of the National Academy of Sciences 117, 1346. In PNAS, Sieh et al. (1) present the best candidate yet for the long-sought source crater of the Australasian tektite strewn field. Unlike the other 4 or so tektite strewn fields, each of which can be traced back to a large impact crater, the Australasian field's source has yet to be definitively located. While this proposal does not ∼ fully prove the case, it offers strong evidence implicating a 15-km-diameter impact crater in Laos that has been hiding in plain sight beneath a mass of younger volcanic rocks. From here, it is clear that the next step in proving its parentage must be drilling through the volcanic rocks into the putative impact rocks below. Tektites are centimeter-scale black or green blobs of glass that have long fascinated humans (2). Moldavites, an Eastern European variety, were found interred with the much more famous Venus of Willendorf, dating back to 30,000 BCE, possibly reflecting our ancestors' interest in unusual rocks as well as female deities. Individual tektites occur in widely strewn fields of which about 4 are currently known (there are other candidate strewn fields). Each of these fields, which extend over hundreds to thousands of kilometers, is associated with a meteorite impact crater - except one, the biggest of them all, the Australasian strewn field. It ranges south from Southeast Asia, across Australia then south of Tasmania to East Antarctica, with a western extension that crosses over Madagascar and an eastern extension into the western Pacific Ocean, covering about 10% of Earth's surface. The tektites in this enormous field have been intensively studied using modern analytical methods. They are divided into a number of distinct types, ranging from meter-scale irregular masses of black glass called Muong Nong …

Mijnendonckx, K., Van Gompel, A., Coninx, I., Bleyen, N., Leys, N., 2020. Water-soluble bitumen degradation products can fuel nitrate reduction from non-radioactive bituminized waste. Applied Geochemistry 114, 104525.

http://www.sciencedirect.com/science/article/pii/S0883292720300068 An important fraction of the currently stored volume of long-lived intermediate level radioactive waste in Belgium is immobilized as Eurobitum. This type of waste typically contains large amounts of NaNO3 homogeneously dispersed in a hard bituminous matrix. Geological disposal of Eurobitum in a water-saturated sedimentary formation such as Boom Clay will result in the leaching of high concentrations of NaNO3 in the Boom Clay formation. This could cause a geochemical perturbation of the surrounding clay, possibly affecting some of the favorable characteristics of the host formation such as its hydraulic conductivity, sorption potential or the redox conditions. The latter might result in a decrease of its reducing capacity and an increase in the mobility of redox-sensitive radionuclides. Microbial nitrate reduction is a well-known process, which could be stimulated by the chemical and radiolytical water-soluble organic bitumen degradation products. The present study carried out different series of long-term anoxic batch experiments to investigate the ability of the microbial community of Boom Clay borehole water to reduce nitrate, leaching from thermally aged non- radioactive Eurobitum in the presence or absence of acetate, formate and oxalate, being part of the most important organic bitumen degradation products. Obtained results indicate that all three organic bitumen degradation products can be used as electron donor to fuel microbial nitrate reduction, albeit with a different efficiency. The highest nitrate reduction rate was observed in the presence of acetate, while oxalate was the least efficient electron donor for nitrate reduction. Moreover, organic compounds that leached from the Eurobitum during the course of the experiment were used as electron donor for microbial nitrate reduction in all conditions. Furthermore, calcium oxalate crystals were observed, indicating that if oxalate is present, it will probably be less bioavailable compared to other organic compounds.